The present invention relates generally to wastewater treatment. More particularly, the present invention relates to methods of cleaning filters used in wastewater treatment by using dispersing agents to disperse the flocculated materials on the filters to automatically loosen any clogging materials and allow for easy removal.
Filter cleaning is a tedious process when filters are clogged by flocculating materials. Especially, when filters are clogged by metal oxides particles, or a mixture of metal oxides and organic flocculating particles, filter cleaning can be very difficult. Prior art cleaning methods for mainly inorganic clogs include acid treatment at pH 2 or less. However, acid treatment methods often require over night soak of the clogged filters. Further, acid treatment alone is often not sufficient for organic flocculating clogs which are usually present with inorganic clogs. Other prior art filter cleaning methods used in wastewater treatment such as alkali treatment, oxidizer treatment, steam cleaning, high pressure liquid cleaning, and detergent washing are also subject to limitations and problems. These treatments require downtime of the filtration system, are costly, and do not address the root of the problem which is clogging by flocculating materials. Accordingly, there is a need for filter cleaning methods that can efficiently remove both organic and inorganic flocculating materials at same time and significantly reduce downtime of the filtration system.
Accordingly, it is an object of the present invention to provide a method of cleaning filters to significantly reduce downtime of the filtration system. It is another object of the present invention to provide a filter cleaning method wherein a dispersing agent can be used alone, or in combination with any other chemical solution to efficiently remove both organic and inorganic flocculated materials clogged on the filters.
In accordance with the present invention, there is provided a method of cleaning filters clogged with flocculated materials. The method comprises determining the nature of flocculated materials clogged on the filter and adding a dispersing agent to break up said flocculated materials to form dispersed precipitates. Then the dispersed precipitates are removed from the filter in a regular cleaning such as backflushing.
The present filter cleaning method can remove both inorganic and organic flocculated materials by using a dispersing agent. The dispersing agent used in the present invention comprises a derivative of polyacrylic acid or other suitable water soluble dispersant. Depending on the nature of the flocculated solid, the dispersing agent can be anionic or cationic or amphoteric. Preferably, the dispersing agent is selected from a group consisting of hydroxy-ethylidene diphosphonic acid, sodium diisopropylnaphthalenesulfonate and other water soluble dispersing agent.
The dispersing agent can be used at a concentration from about 10 to 100 ppm. The dispersing agent can be used alone, or in a mixture with an acid or oxide. The pH of the dispersing agent solution can be in a range from about 2 to 7.5.